Catheter shaft comprising welded tubes

ABSTRACT

One embodiment of the invention relates to a catheter shaft comprising (i) a first tube made of an extrudable copolymer that has reactive groups, and (ii) a second tube made of a polymeric material, which can be welded to the first tube, wherein the polymeric material of the second tube can be welded to the first tube at a temperature ≦200° C.

CROSS REFERENCE

The present application claims priority on co-pending U.S. ProvisionalApplication No. 61/617,059 filed on Mar. 29, 2012; which application isincorporated herein by reference.

TECHNICAL FIELD

A field of the invention is catheters. Another field of the inventionrelates to a catheter shaft comprising a first (inner and/or outer) tubemade of an extrudable, fluorinated copolymer and a second tube made of apolymeric, preferably thermoplastic, material, which is welded to thefirst tube.

Another field of the invention further relates to a medical devicecomprising such a catheter shaft, and the use of a first tube made of anextrudable, fluorinated copolymer to be welded to a second, polymerictube. Another field of the invention also relates to a method formanufacturing a catheter shaft or a medical device comprising therelated tubes and a certain, particularly suitable tube.

BACKGROUND

On the market today, multi-layer tubes are used for the inner shaft of acatheter. They include, for example, multi-layer polytetrafluoroethylene(PTFE) tubes, co-extruded HDPE (high density polyethylene) tubes and thelike, which comprise a polyamide-based outer layer to permit these innershafts to be welded to other tubes that have a second tube layer made ofa polymeric, thermoplastic material.

Fluorinated polymers (e.g., PTFE) generally have the lowest coefficientsof friction relative to other materials, are resistant to ageing and arehighly resistant to chemicals. Disadvantages of PTFE are the complexmanufacturing process of tubes (not by conventional extrusion since PTFEcannot be processed thermoplastically because PTFE is not fusible) andthe low abrasion resistance. Another disadvantage of PTFE-based innertubes is the high price and the dependence on certain manufacturers. Afurther disadvantage of PTFE as a material for medical devices is thatPTFE cannot be sterilized using radiation sterilization methods.

Other thermally deformable (extrudable), fluorinated polymers that alsohave low coefficients of friction (for example, ETFE(polytetrafluorothylene+ethylene, E-CTFE(polychlorotrifluoroethylene+ethylene), PFA(polytetrafluoroethylene+perfluoropropylether), FEP(polytetrafluoroethylene+perfluoropropylene), PCTFE(polychlorotrifluoroethylene), PVF (polyvinyl fluoride) and PVDF(polyvinylidene fluoride)) cannot be welded to the established catheterpolymers (such as polyamide 12 or PEBA, for example), which are used forouter shafts, tips and balloons, for instance, and are very difficult tobond due to the low surface tension and resulting reduced wettability.

For this reason, only highly complex, multi-layer tube structures havebecome established for use as inner shafts for RX catheters (withreduced friction with respect to guide wires), for example. Tubes areknown, inter alia, which have PTFE as the inner layer and apolyamide-based outer layer or multi-layer structures having an HDPEinner layer and, likewise, a polyamide-based outer layer.

The disadvantage of co-extruded inner shaft designs based on HDPE, forexample, is also the expensive manufacturing process by co-extrusion ofat least two, typically three layers, in which one extruder is used foreach layer.

Document US 2010/0063476 A1 describes the use of modified PVDF as theinner layer of co-extruded tubes. Co-extrusion requires the use ofhighly complex equipment and requires working with at least two,typically three separate extruders, which must be matched to oneanother, to ensure that the two or three co-extruded layers have thedesired layer thickness distributions in the final tube dimensions. Thetemperatures of the separate extruders must be selected such that thedifferent tube layers are connected to one another during extrusion,which, in the case of a 3-layer extrusion, typically takes place by wayof a physical connection between the HDPE inner layer to the middlelayer and by way of a chemical connection of the middle layer to thepolyamide-based outer layer. The pressure and temperature requirementsare therefore high. Co-extrusion results in covalent bonding of the twotube layers, which is absolutely desired.

SUMMARY

One of the problems addressed by the invention was that of providingcatheter shafts that could be manufactured more easily, at a lower cost,that preferably have the lowest possible coefficient of friction, andpreferably have high chemical resistance and/or high ageing resistance.In addition, through methods of the invention it is possible to weldthese shafts to typical polymer-based catheter components, in particularcomponents based on polyamide. A further preferred property is for thecomponents to be effectively sterilizable using radiation.

This and other problems are solved by a catheter shaft comprising (i) afirst (inner and/or outer) tube made of an extrudable copolymer that hasreactive groups, and (ii) a second tube made of a polymeric material,which can be welded to the first tube, wherein the polymeric material ofthe second tube can be welded to the first tube at a temperature ≦200°C.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows the pushability (force transmission) on coronary balloondilation catheters comprising

a) a balloon dilation catheter having an inner shaft according to theinvention

b) balloon dilation catheter having a co-extruded inner shaft with Thefigure therefore shows a comparison of the mechanical forces that play arole in the forward motion of a catheter shaft according to theinvention, compared to a shaft according to the prior art.

FIGS. 2 a and 2 b show the trackability (frictional forces) on coronaryballoon dilation catheters in an aorta model with a Teflon® tube as thefriction partner. Guide wire: Galeo M ″014; guide catheter: Cordis Vista5F JL 4LBT

a) a balloon dilation catheter having an inner shaft according to theinvention

b) a balloon dilation catheter having a co-extruded inner shaft (US2010/0063476 A1

FIGS. 2 a and 2 b therefore present corresponding data on friction.

FIG. 3 is a schematic drawing of the design of a catheter comprising aninner shaft according to the invention

FIG. 4 is a schematic drawing of the welding of the outer shaft andinner shaft

FIG. 5 is a schematic drawing of a distal balloon welding at a cathetershaft according to the invention

FIG. 6 is a schematic drawing of the proximal welding of a distalcatheter according to the invention to a hypotube

FIG. 7 is a schematic drawing of a proximal balloon welding

DETAILED DESCRIPTION

Before discussing various example embodiments and features of theinvention, some discussion of definitions of terms used in suchdescription will be useful. It will be appreciated that unless otherwisestated, terms are intended to have their ordinary meaning in thebroadest sense.

Reactive groups are molecular groups that have a higher reactivity tonucleophiles than methyl or methylene groups. Within the scope of theinvention, reactive groups preferably have at least the reactivity of acarbonyl group, particularly preferably from a carbonic acid derivativegroup, most particularly preferably from a carbonic acid anhydridegroup, with respect to nucleophilic agents, preferably with respect to ahydroxy and/or amine group. A copolymer within the scope of the presentinvention can already be present if only reactive groups areincorporated into a classical polymer parent structure. It is alsopossible, in principle, for side chains carrying the more reactivegroups to be bound to the polymer parent structure, preferably beinggrafted thereto.

Within the scope of the present invention, welding means that two layers(in this case, the outer layer of one tube and the inner layer ofanother tube in particular), which are substantially in the solid state,are covalently bound by the (relatively brief) effect of heat. Withinthe scope of the invention, it is not ruled out that (brief) softeningcaused by fusion takes place in the region of the interfaces of the twolayers.

Within the scope of the invention, welded means that at least one spotweld is present, that is, the first and second tubes within the scope ofthe present invention do not need to be welded to one another in a flatmanner, but rather that spot welded connections are sufficient withinthe scope of the invention (although in some embodiments “welded” mayrefer to flat welding of two pieces to one another). Welded connectionsare preferable, however, which interconnect at least the entirecircumference in the region of a tube section (that is, of a part of thelongitudinal extension of the tube). This means that, strictly speaking,the lumen of the outer tube welded to the inner tube no longer needs tobe continuous.

Within the scope of the present invention, extrudable means that the(dried) material (preferably a thermoplastically shapable polymer orcopolymer) can be fused in a single-screw extruder having a diameter of12 to 30 mm and a length-to-diameter ratio (L/D) of 24 to 28 attemperatures that are 50° C. to 100° C. higher than the melting point ofthe thermoplastic polymers, the polymer melts are conveyed to a shapingpart (extrusion head) comprising a nozzle, which shapes the outer tubelayer, and a mandrel, which shapes the inner tube layer, and can bebrought into a permanent shape by “quenching” the shaped polymer meltsin a water bath.

It has been shown that suitable modified fluorinated polymers(copolymers) are capable of bonding with sufficient strength to aplurality of preferably thermoplastic, polymeric materials thatpreferably have nucleophilic groups. In the prior art, such compoundswere regularly created by co-extrusion, however. Through the presentinvention it has been discovered, surprisingly, that it is possible toweld a hardened tube made of a fluorinated copolymer comprising reactivegroups to a plurality of suitable second separate tubes at temperatures≦200° C. Before the inveiont, it was assumed that the appropriatematerials could only be bound to one another in an adequate manner byway of co-extrusion which added significant cost, time and effort ascompared to embodiments of the invention.

Preferably at least the first tube, but further preferably both tubes,are present as separate tubes when welding takes place. Weldingpreferably takes place over the greatest possible surface area, whichmeans that the two tubes have different diameters, thereby enabling onetube to be slid into the other tube (although in some embodiments localspot weld connections may be used). The inner diameters and wallthicknesses of the tubes must be suitably matched to one another, withat least some embodiments including an outer tube inner wall surfacecontacting the inner tube outside wall surface and other embodimentsallowing for some suitably small gap between walls to exist. A flat weldalong the outer circumferential surface (of the inner tube) or the innercircumferential surface of the outer tube is preferable.

The invention relates to the configuration in which the first tube isattached to the outer tube, and to the configuration in which the firsttube is the inner tube. Further layers and/or tubes are present in otherembodiments, although in many applications the catheter shaft willcomprise only the first tube and the second tube.

On the basis of the present application it is possible for a personskilled in the art to match materials and welding surface sizes suchthat the weld points are highly stable. Within the scope of theinvention, however, these welds are preferably designed such that theyresist, without changing, a balloon pressure of 20 bar, preferably 24bar, for ≧1 min, preferably ≧2 min, particularly preferably ≧10 min. Aperson skilled in the art will also take the entire geometry of the weldsurfaces into account for this purpose.

According to one embodiment of the invention, a catheter shaft ispreferred, wherein the fluorinated copolymer is a thermoplasticcopolymer on the basis of a polymer selected from the group comprisingETFE, C-ETFE, PFA, FEP, PCTFE, PVF and PVDF.

A changed PVDF that has been modified preferably by the grafting ofmaleic acid anhydride is particularly preferred in this context.

Documents AU 2004/202463 B2 and EP 1 484 346 and US 2010/0255378 A1 alldisclose copolymers of fluoropolymers (modified fluoropolymers), atleast some of which are examples of materials that may be useful inpractice of some invention embodiments. These documents are incorporatedherein by reference to the extent necessary and possible as examples ofmaterials that may be useful to practice some invention embodiments.Those knowledgeable in the art will appreciate many such materials asgenerally described herein are available, and detailed descriptionthereof is not necessary for sake of brevity.

The aforementioned materials are suitable in particular due to theirchemical resistance and their low coefficient of friction. Theaforementioned copolymers can be extruded as the first tube, and can beused as either the inner tube or the outer tube, depending on theintended use of the catheter shaft or the medical device comprising saidcatheter shaft. Extrusion may be single extrusion of a single layertube.

In general, thermally deformable, fluorinated polymers are preferred, inaddition to the explicitly named fluorinated polymers, for the firsttube (in a related modification).

Preferred reactive groups in the fluorinated copolymer for bonding tothe second tube are in the groups (chemical functions) selected from thegroup comprising carbonic acid, carbonic acid chloride, amide, carbonicacid anhydride, ester, lactone, lactam, nitrile, and thioester.

By way of these reactive groups, nucleophilic attacks on the polymericmaterial of the second tube are well ensured, and therefore a pluralityof material combinations is possible.

Within the scope of the present invention it is preferable for thesecond tube to be selected from the group of polyamide, PEBA (polyetherblock amide), polyester, thermoplastic polyurethane elastomers (TPU).

In general, thermoplastic polymers are preferred for the second tube.

As indicated above, it has surprisingly been discovered that themodification of the fluorinated polymers makes it possible to establisha reliable connection to the polymers of the second tube. Within thiscontext it was surprising, however, as likewise indicated above, thatwelding can be carried out even under relatively mild conditions, andthat co-extrusion is not absolutely necessary (although it may be usedin some invention embodiments).

Further material combinations are usable due to the invention, therebyproviding a person skilled in the art with more possibilities withrespect to the prior art for adapting the catheter shaft or medicaldevices containing them to the particular requirements. It is possible,for example, to design the inner shafts for RX catheters (with reducedfriction with respect to guide wires) without the need for complexmulti-layer tube structures comprising intermediate primer layers. Thereis also a good alternative to PTFE as the inner layer, and there arealternatives to the typical HDPE inner layers on the market. Valuablebenefits, including cost savings and improved performance, are therebyachieved over the prior art.

The mechanical properties of the complete system can also be improved byway of the combination according to the invention.

Turning now to the drawings by way of further illustration, compared toa balloon dilation catheter having a co-extruded HDPE inner shaft, a(balloon dilation) catheter according to the invention has a highertransmission of the force applied at the proximal end onto the distalend of the catheter (FIG. 1).

FIG. 2 a shows a comparison of the frictional forces of a balloondilation catheter according to the invention with those of a balloondilation catheter of the prior art according to US 2010/0063476 A1. Thetwo balloon dilation catheters are identical except that the innershafts are different. In this test, the catheters are introduced invitro in a model that corresponds to a simulation of a coronary artery,and the required proximal force is determined. The balloon dilationcatheter according to the invention requires much less force than thecatheter according to US 2010/0063476 A1, which indicates lower frictionin the case of the inner shaft according to the invention compared tothe catheter according to US 2010/0063476 A1. The balloon dilationcatheter according to the invention also exhibits slighly improvedfrictional forces compared to a catheter comprising a co-extruded HDPEinner shaft according to the prior art (FIG. 2 b). This illustrates afew of the many valuable benefits and advantages embodiments of theinvention achieve over the prior art.

According to the above-cited tests, a first tube is particularlypreferred, according to the invention, for a single-layer catheter shaftmade of a PVDF grafted with maleic acid anhydride, which is fused in aconventional single-screw extruder (Ø 12-30 mm / L/D 24-28) and isshaped into a tube by way of a shaping part. The shaped melt is quenchedin a water bath. The second tube, which can be welded to the first tube,comprises a polyamide layer, preferably an (initially) separate tube.

A fluorinated copolymer that may be used includes polyvinyldene fluoride(PVDF). In some applications, a functionalzed PVDF is used that has areactive group. A useful example is the material with the trade name“Kynar® ADX” from the company Arkema Inc., (King of Prussia, Pa.). Tubescan be produced from this material by extrusion at low cost.

Kynar ADX was developed by Arkema for the co-extrusion of PVDF withpolyamide 12, for automobile fuel lines, for example. Kynar ADX is afunctionalized polyvinylidene fluoride, which can enter into a chemicalbond with thermoplastic polymers, such as polyamide, PEBA, polyester,TPU, etc. The reactive functional groups of maleic acid anhydride areintroduced into the original PVDF by compounding and slight irradiationcross-linking. In US 2010/0063476 A1, this material is used for theco-extrusion of a two-layer tube in accordance with the manufacturer'sfield of application.

The chemical modification of a PVDF such as Kynar ADX is intended toproduce a chemical bond when two polymer melts meet in the co-extrusionprocess, for example, in is which the maleic acid anhydride of the KynarADX is attacked by way of nucleophilic groups of the second layer,wherein at least one amide bond, preferably an imide bond, is produced.

Surprisingly, tubes made of a functionalized PVDF such as Kynar ADX canalso enter into a chemical bond with other polyamide-based components(welding) after thermal treatment. That is, the chemical modificationalso functions after extrusion and the immersion of the shaped Kynar ADXmelts associated therewith in water. This is previously unknown for thismaterial since the maleic acid anhydride groups at the tube surface,which have contact with water, are saponified to form less reactivedicarbonic acid groups. By slightly fusing the surfaces of the twoelements to be joined (the first and second tubes in this case), acovalent chemical bond is created between the two elements to be joined.This is sufficient to weld the various components to one another.

PVDF also has better radiation sterilizability than PTFE (maximumradiation dosage PVDF 1500 kGy, Teflon <20 kGy).

These first tubes according to the invention, which are made of PVDF,can be used as the inner tube for RX catheters, for example (although insome other example embodiments they can be the outer tube). They can bechemically welded proximally with a polyamide-based outer shaft anddistally to a polyamide-based balloon and/or tips, in particular by wayof a laser or thermal energy.

Alternatively, it is also possible to use the corresponding first tubeas the outer tube for RX catheters without coating, or as the outer tubefor self-expandable stent delivery devices. In this case, the lowfriction of the material is utilized toward the outside in particular.The advantages of the catheter shafts according to the invention to beemphasized in particular are, therefore:

-   -   Single extrusion of the first tube can be carried out without        co-extrusion. This results in considerable cost savings, in        particular with regard to the extrusion devices and conditions.    -   The friction of the first tubes (in particular in the preferred        shapes) is greatly improved (reduced) in the form of an outer        tube and as an inner tube within a catheter tube.    -   The mechanical properties related to introducibility are        improved.    -   Reliable sterilization by radiation is possible.    -   The first tube made of modified PVDF can be welded to        polyamide-based second tubes by way of chemical binding.

Moreover, it is possible to easily weld further components to thecatheter shaft.

Part of the invention is therefore a medical device comprising acatheter shaft, as described above.

Particularly preferably, such a medical device is selected from thegroup comprising a catheter stent insertion device or a balloon dilationcatheter, in particular in an RX (rapid exchange) or “over the wire”design.

Part of the invention is also a (first) tube made of a PVDF grafted tomaleic acid anhydride as the reactive group, which was fused, inparticular, in a conventional single-screw extruder (Ø 12-30 mm/L/D24-28) and shaped into a tube by way of a shaping part, and which can bewelded in particular to a second polyamide-based tube, a separate tube,as a component of a catheter shaft according to the invention or amedical device according to the invention.

In the case of the material that is used particularly preferablyaccording to the invention, although a scientific basis for thediscovery is not presently known with certainty, it is believed that thereactive group (maleic acid anhydride) is hydrated in water after isextrusion, and therefore a chemical reaction with amino groups, forexample, is possible even when welding is performed at ≦200° C., and inothers less than 190° C., and in some embodiments at pressures less than200 bar, others less than 180 bar, in contradiction to the acceptedpractice of the prior art (as indicated, for instance, by a PVDFmanufacturer's claim). Prior to the present invention it was believedthat temperatures >220° C. and pressures in the range of 200 bar wererequired to ensure reliable bonding of the material to a correspondingsecond tube. Under these conditions, the maleic acid anhydride reactswith amino groups of a polyamide and forms chemical imide compounds.

Using methods of the invention, however, this is not necessary. Whenwelding is carried out in an invention embodiment, a carbonic acidfunction reacts with the amine to form an amide group. Therefore, onlyslight fusing is required during welding (T≦200° C.), wherein a shrinktube is preferably used in principle for welding, in order to press thetubes onto one another.

Compared to the prior art, this has the following valuable benefits andadvantages (among others):

In the 3-layer co-extrusion of HDPE/primer/polyamide inner tubes, thethree different materials are fused in three different extruders atdifferent temperatures. The three polymer melts are guided to a shapingpart (co-extrusion head), where the three polymer melts meet. A physicalbond is produced between the HDPE and the primer layer, and a chemicalbond is produced between the polyamide layer and the primer layer. Inthis design, the HDPE inner layer serves to minimize friction withrespect to the guide wire. The primer layer joins the HDPE inner layerwith the polyamide outer layer. The polyamide outer layer serves forbonding with other polyamide-based tubes, tips or balloon (=component tobe welded thereto). The same mode of operation also takes place in theco-extrusion of the inner shaft in the laid-open application US2012/0063476 A1. In this case, the inner layer is made of thefluorinated modified polymer PVDF, which is bonded to thepolyamide-based outer layer by way of the chemical modification in theco-extrusion. The PVDF inner layer serves to reduce the friction withrespect to the guide wire, and the polyamide-based outer layer serves toensure weldability to further polyamide-based tubes, balloons or tips. Aphysical welding of the two elements takes place, in which physicalintermixing takes place by way of the fusion of the two surfaces to beconnected.

In the extrusion of the modified PVDF according to some embodiments ofthe invention, only one single-layer tube is extruded, that is, theinner surface and outer surface of the tube is made of the modifiedPVDF. The welding with further catheter components (such as furthertubes, balloons or tips) takes place by way of the chemical reaction ofthe maleic acid anhydride groups contained therein or the maleic acidgroups that form with nucleophilic groups contained in the polymers ofthe separate welding partner. The two surfaces to be joined aretherefore chemically interconnected by way of amide or imide bonds, andexhibit no intermixing.

In the conventional inner shaft design having physical intermixing ofthe two surface materials, the welding partners therefore differfundamentally from the chemical welding of the two surface materialsaccording to the invention (without intermixing of the two materials).

As described above, the catheter shafts according to the invention—and,therefore, medical devices according to the invention—have bettertrackability with respect to a catheter having a conventionalthree-layer HDPE inner shaft. Moreover, the transmission of force ontothe distal end of the catheter is markedly increased compared to theconventional three-layer HDPE inner shaft. As a result, the dimensions(outer diameter) of the inner shaft can be reduced without making greatsacrifices with respect to force transmission. In addition, the profileof crimped stents of stent delivery RX catheters is reduced.

Furthermore, it has been discovered that it is easily possible toreliably weld further components to the catheter shaft design accordingto the invention, such as distal balloons. In the catheter obtained inthe example (see below), the distal balloon neck withstands pressures ofat least 24 bar after being welded to the first tube (which was designedas an inner shaft) to be used according to the invention. The balloonburst at this pressure. This corresponds to an approximate minimaltension at the weld of 230-240 N/mm².

The increased force transmission (pushability) compared to conventionalRX catheters having three-layer inner tubes (HDPE-Tie-PA or PEBA)improves the usability of the catheter shafts according to the inventionor the medical devices that comprise said shafts.

If the first tube to be used according to the invention is used as adistal outer shaft, lower frictional properties exist without the needto apply an additional, complex and expensive coating.

Since sterilization by radiation is possible, the catheter shaftsaccording to the invention can also be used for drug-coated cathers(drug-eluting stents or drug-eluting balloons), for example, in the caseof which the drug that is applied cannot be sterilized by ethyleneoxide.

According to the statements provided above, part of the invention is theuse of a first tube, as defined above, for welding to a second tube, aslikewise described above, to produce a catheter shaft according to theinvention or a medical device according to the invention.

This usage achieves the above-described advantages as well as others.

Another part of the invention is a method for the manufacture of acatheter shaft according to the invention or a medical device accordingto the invention, comprising the steps:

a) provide a first tube as defined above,

b) provide a second tube as defined above and

c) weld the first tube to the second tube.

By way of this method, the catheter shafts according to the inventionand the medical devices according to the invention can be produced in alow-cost and reliable manner.

A method according to the invention is preferred, wherein welding takesplace at a temperature ≦200° C.

These welding conditions are relatively mild, and it is therefore easilypossible to produce the products according to the invention.

Moreover, a method according to the invention is preferable, wherein thefirst tube is provided by conventional tube extrusion with cooling ofthe shaped layer in water. PVDF grafted with maleic acid anhydride ispreferably used, which, in turn, is preferably fused in a conventionalsingle-screw extruder (Ø 12-30 mm/L/D 24-28) and shaped by way of ashaping part into a tube, which is quenched in a water bath.

As described above, when several reactive groups are present, inparticular maleic acid anhydride, this mode of operation results inincreased reactivity and, therefore, improved weldability even if thenon-hydrated anhydrides are more reactive to nucleophiles than thedicarbonic acid groups that are produced.

Even further preferred is a method according to the invention, whereinthe welding takes place by the effect of heat for 3-20 seconds, morepreferably for 5-15 seconds.

This welding period is sufficient, and therefore a relatively rapidmethod for producing the objects according to the invention is madepossible.

According to the invention, a method according to the invention isfurthermore preferred in which welding takes place by way of heatingjaws, laser, white light or vibration.

These are common means for welding which are easy to use and can be usedextremely well for a number of variant applications.

EXAMPLES

Some example embodiments and features of the invention are explained ingreater in the following with reference to examples and the relatedfigures.

The figures show:

FIG. 1 the pushability (force transmission) at coronary balloon dilationcatheters

FIGS. 2 a and 2 b the trackability (frictional forces) at coronaryballoon dilation catheters in an aorta model with a Teflon® tube as thefriction partner

FIG. 3 a schematic drawing of the design of a catheter comprising aninner shaft according to the invention

FIG. 4 a schematic drawing of the welding of the outer shaft and innershaft

FIG. 5 a schematic drawing of a distal balloon welding at a cathetershaft according to the invention

FIG. 6 a schematic drawing of the proximal welding of a distal catheteraccording to the invention to a hypotube

FIG. 7 a schematic drawing of a proximal balloon welding

The first tube was typically extruded from a chemically modified PVDF(e.g., Kynar ADX 1740-15 (PA) from Arkema) on a conventionalsingle-screw extruder (e.g., Ø 12-30 mm with a L/D ratio of ˜24).

1. Extrusion of a Single-Layer Tube to be Used According to theInvention

The granulate Kynar ADX 1740-15 (PA) was dried in a compressed air drier(dew point −30° C.) for 4-6 h at 70-100° C.

The dried granulate was metered into the extruder by way of the intakezone of a single-screw extruder (Ø 12-30 mm, L=24-28 D) and fused in theextruder at the temperatures is proposed by Arkema. The melts wereconveyed out of the extruder by way of an extrusion head comprising anozzle and a mandrel, and the tube shaped in this manner was calibratedto the desired final tube dimension, wherein a draw-rate balance ofapproximately ˜1.0 and a deep-draw ratio of 8-10 were used.

The resulting tube was characterized by tension testing:

-   -   Yield stress: 46N/mm²    -   Yield strain: 6%    -   Stress at failure: 100N/mm²    -   Percent elongation at failure: 254%    -   Modulus of elasticity: 1120 N/mm²

2. Welding of Inner Shaft Tube/Outer Shaft Tube

FIG. 3 shows a schematic depiction of a catheter shaft according to theinvention (catheter with an inner shaft according to the invention). Thereference characters mean:

-   -   1 first tube (inner tube)    -   2 second tube (outer tube)    -   3 guide wire outlet point    -   4 auxiliary wire

After the first tube 1 produced according to 1.) was inserted into thesecond tube 2 by way of the guide wire outlet point 3 thereof, anauxiliary wire 4 was inserted into the first tube 1.

FIG. 4 presents a schematic depiction of the procedure for welding thefirst tube and the second tube (outer tube and inner tube) together. Thereference characters mean:

-   -   1 first tube    -   4 auxiliary wire    -   5 Si tube to prevent the outer tube 2 from fusing with the        welding jaw 6.    -   6 welding jaw

The first tube 1 (inner tube) was welded to the second tube 2 (outertube) using the welding jaw 6 at welding jaw temperatures of 185-205° C.for 5-15 seconds.

3. Distal Balloon Welding

FIG. 5 presents a schematic depiction of the welding of a distal balloonto the catheter shaft according to the invention. The referencecharacters mean:

-   -   1 first tube    -   4 auxiliary wire    -   7 balloon    -   8 shrink tube    -   9 tip    -   10 flush lay edge

A suitable auxiliary wire 4 was inserted into the first tube 1. Aso-called tip 9 made of polyamide was positioned on said auxiliary wireon the distal end of the first tube 1 (inner shaft). The distal balloonneck was positioned by way of the distal end of the first tube 1 and theproximal end of the tip 9. A shrink tube 8 was positioned by way of thedistal balloon neck. The distal balloon neck was welded using a laserhaving a power of 20-25 watts within 4-7 seconds onto the first tube 1and the tip 9, wherein the region to be welded rotated in the axialdirection at 1,500-2,500 rpms.

4. Welding the Guide Wire Outlet Points

The distal part produced according to 3.) was now connected to theproximal part of a hypo tube. This is depicted schematically in FIG. 6.The reference characters mean:

-   -   8 shrink tube    -   11 front part of the catheter    -   12 hypotube

To this end, the second tube 2 was slid with the first tube 1 onto thehypotube encased in polyamide by way of a shrink tube. The second tube 2was then welded using welding jaws for 8-20 seconds at 215-235° C. Atthe same time, the first tube 1 was also welded to the second tube 2.

5. Proximal Balloon Welding

FIG. 7 shows the proximal balloon welding in a schematic depiction. Thereference characters mean:

-   -   1 first tube    -   2 second tube    -   7 balloon    -   8 shrink tube

An appropriate wire was inserted into the second tube 2 and the proximalballoon neck was positioned on the distal end of the second tube 2(outer shaft). A shrink tube 25 was positioned over the point to bewelded. A balloon neck was welded onto the second tube 2 using a laserfor 1 to 4 seconds with an energy of 15 to 25 watts. Next, the shrinktube was removed.

All of the welds created above were checked in a pressure test. None ofthe welds described failed, having been exposed to pressures of at least24 bar.

It will be apparent to those skilled in the art that numerousmodifications and variations of the described examples and embodimentsare possible in light of the above teaching. The disclosed examples andembodiments are presented for purposes of illustration only. Otheralternate embodiments may include some or all of the features disclosedherein. Therefore, it is the intent to cover all such modifications andalternate embodiments as may come within the true scope of thisinvention.

What is claimed is:
 1. A catheter shaft comprising (i) a first tube madeof an extrudable fluorinated copolymer that has reactive groups, and(ii) a second tube made of a polymeric material, which is welded to thefirst tube, wherein the polymeric material of the first and second tubesare configured to achieve welded attachment with welding performed at atemperature ≦200° C.
 2. The catheter shaft according to claim 1, whereinthe fluorinated copolymer is a copolymer of a polymer selected from thegroup comprising ETFE, C-ETFE, PFA, FEP, PCTFE, PVF and PVDF.
 3. Thecatheter shaft according to claim 1, wherein the reactive groups areselected from the group comprising carbonic acid, carbonic acidchloride, amide, carbonic acid anhydride, ester, lactone, lactam,nitrile and thioester.
 4. The catheter shaft according to claim 1,wherein the polymeric material of the second tube is selected from thegroup comprising polyamide, PEBA, polyester or TPU.
 5. The cathetershaft according to claim 1, wherein the first tube is made of PVDFgrafted with maleic acid anhydride as the reactive group, and the secondtube is made of polyamide 12 or PEBA.
 6. The catheter shaft according toclaim 1, wherein the tubes remain welded to one another, unchanged, at apressure of 20 bar for ≧1 min
 7. The catheter shaft according to claim1, wherein the catheter shaft is included in a medical device.
 8. Themedical device according to claim 7, selected from the group comprisinga catheter stent insertion device or a balloon dilation catheter, inparticular in an RX (rapid exchange) or over the wire design.
 9. Amethod for manufacturing a catheter shaft comprising the steps: a)provide a first tube made of a fluorinated copolymer with at least areactive group, b) provide a second tube made of a polymeric material,and c) welding the first tube and the second tube to one another.
 10. Amethod according to claim 9, wherein the step of welding is performed ata temperature ≦200° C.
 11. The method according to claim 9, wherein thestep of providing a first tube further comprises conventional tubesingle extrusion of the first tube followed by cooling of the formedtube in water.
 12. The method according to claim 9, wherein the step ofwelding includes applying heat energy for 3 to 20 seconds.
 13. Themethod according to claim 9, wherein the step of welding includes usingone of heating jaws, light or vibration and results in the formation ofchemical bonds between the inner and outer tubes.
 14. The methodaccording to claim 9 wherein: the first tube is made of a single layerof the fluorinated copolymer; the fluorinated copolymer is a copolymercomprising one of ETFE, C-ETFE, PFA, FEP, PCTFE, PVF and PVDF; thereactive group comprises one of carbonic acid, carbonic acid chloride,amide, carbonic acid anhydride, ester, lactone, lactam, nitrile andthioester; the second tube comprises one of polyamide, PEBA, polyesteror TPU; and, the step of welding causes surfaces of the inner and outertubes to be joined through formation of chemical bonds withoutintermixing of materials from the inner and outer tubes.
 15. The methodaccording to claim 9, wherein: the first tube comprises a PVDF with areactive group and is configured as the catheter inner tube; and, thesecond tube comprises a polyamide and is arranged as the catheter outertube.
 16. The method according to claim 9 wherein: the first tubereactive group comprises maleic anhydride; wherein the step of providingthe first tube further comprises extruding the first tube followed byquenching in water to result in saponifying the maleic anhydride groupsto a less reactive dicarbonic acid groups; and, wherein the step ofwelding causes a chemical bond to be formed between the dicarbonic acidgroups of the first tube and the polyamide groups of the second tube.17. A catheter shaft as defined by claim 1 wherein the first tube ismade of PVDF grafted with maleic acid anhydride as the reactive group.18. A method for making a catheter shaft comprising the steps of:extruding a first tube having a single layer made of PVDF with at leasta reactive group; cooling the first tube following extrusion by exposureto water; providing a second tube comprised of a polyamide; and, joiningthe first and second tubes and applying heat to adjoin portions of thefirst and second tubes to cause a chemical bond to be created betweenthe first and second tubes to thereby attach the first and second tubesto one another.
 19. A method for making a catheter shaft as in claim 18wherein: the reactive group comprises maleic anhydride; the step ofcooling the first tube by exposure to water further comprisessaponifying the maleic anhydride groups to a less reactive dicarbonicacid groups; the step of applying heat causes the chemical bonds to beformed between the dicarbonic acid groups of the first tube andpolyamide groups of the second tube.
 20. A method for making a cathetershaft as in claim 19 wherein the step of applying heat comprises weldingthe adjoining portions at a temperature of no more than 200° C. and atime period of no more than 20 seconds.